1. Field of the Invention
The present invention relates to an electric motor.
2. Description of the Related Art
Some known motors for use in storage disk drives include a bearing mechanism utilizing a fluid dynamic pressure. For example, a fluid dynamic bearing apparatus for use in a spindle motor disclosed in JP-A 2010-121775 includes a base plate, a first bearing component, a second bearing component, a shaft, and a bearing sleeve. The first bearing component is accommodated in an opening portion of the base plate. A lower portion of the shaft is fixed to a central opening portion of the first bearing component. The second bearing component is annular, and is arranged on an upper portion of the shaft. The bearing sleeve is arranged around the shaft and the second bearing component to be rotatable relative to the shaft and the second bearing component.
A second seal gap and a liquid reservoir portion are defined between radially opposing surfaces of an upper portion of the bearing sleeve and the second bearing component. The liquid reservoir portion is arranged on an upper side of the second seal gap. The first bearing component includes a portion arranged radially outward of a lower portion of the bearing sleeve to extend upward. A first seal gap is defined between radially opposing surfaces of this portion and the bearing sleeve. When a bearing fluid is fed into the fluid dynamic bearing apparatus, the bearing fluid is poured into the liquid reservoir portion and the second seal gap. The fluid dynamic bearing apparatus is then allowed to remain stationary for tens of minutes, and during this time the lubricating fluid travels through a bearing gap defined between the shaft and the bearing sleeve to reach and spread throughout the first seal gap.
The “Background Art” section of JP-A 2010-121775 describes a related-art technique of supplying a bearing fluid into end opening portions at both ends of a bearing gap by using a feeding apparatus with a work space placed under reduced pressure, and thereafter supplying air into the work space to cause the bearing fluid to be sucked into the bearing gap. JP-A 2010-121775 mentions that this related-art technique has a problem in that it is difficult to supply a sufficient amount of the bearing fluid to the end opening portion at a lower end of the bearing gap since this end opening portion is normally covered with a hub or a bearing sleeve. This difficulty may lead to a surface of a bearing (i.e., a fluid dynamic bearing apparatus) being smeared with the bearing fluid.
Meanwhile, the above-described operation of feeding the bearing fluid into the fluid dynamic bearing apparatus as disclosed in JP-A 2010-121775 has problems in that the feeding of the lubricating fluid into the bearing gap may not be completed in a short time, and that an air bubble may be introduced into the bearing gap during the feeding of the bearing fluid.